Probably too late to answer but this is an interesting topic (to me anyways).
I don't give a darn whether Shinichi ends up with Ran or sewer rats, as long as they didn't just toss Ai aside. What I'm worried about is that Ai ends up being forgotten while ShinRan rode unicorns to happy sunset. Or worse, never again mentioned after the 'BO battle' everyone know will be there sooner or later, in any form. I'll be severely pissed if that Gosho made it like that.
At the least (even if CoAi didn't come true), Shinichi will be shown working on a case with Shiho, throwing witty remarks as usual. This will be satisfying, even if it's only a short scene.